last week I noticed my Firebird 2.5 packages started to fail building
for openSUSE Factory. A bit surprisingly this is not caused by the
switch to gcc7 but by an upgrade of ICU to 59.1.
According to their release notes, ICU 59.1 requires C++11 to build. An
immediate symptom is an error about unknown type uchar16_t. This would
be probably easy to work around but there may be more subtle issues.
It's only a problem for Firebird 2.5 as 3.0 and newer use C++11 mode by
default anyway. For 2.5, though, most gcc6 compatibility issues were
worked around by enforcing C++98 mode (-std=gnu++98).
It's probably nothing really serious as distributions which are new
enough to provide ICU 59.1 most likely already have Firebird 3.0 which
is fine; I just wanted to give a heads up to save others time if they
run into this issue.